In communications networks, there may be a challenge to obtain good performance and capacity for a given communications protocol, its parameters and the physical environment in which the communications network is deployed.
For example, evolving services are associated with new requirements on cellular networks, e.g. with respect to device cost, battery lifetime and coverage. To drive down device and module cost, a system-on-a-chip (SoC) solution with integrated power amplifier (PA) can be used. However, it is feasible for the current state-of-the-art PA technology to allow 20-23 dBm transmit power when PA is integrated to SoC. This constraint limits uplink coverage, which is related to how much the path loss is allowed between the end-user wireless device and network node of the communications network.
To maximize the coverage achievable by an integrated PA, it is commonly necessary to reduce PA backoff. PA backoff may be defined as the ratio of maximal saturation output power and average output power of the PA. PA backoff is needed when the communication signal has significant non-unity peak-to-average power ratio (PAPR). The higher the PAPR is, the higher PA backoff is required. Higher PA backoff also gives rise to lower PA efficiency, and thus lower device battery life time. Thus, designing an uplink communication signal that has as low PAPR as possible—and thereby reduces the necessary PA backoff—could lower the device cost, increase the battery lifetime and increase the coverage of the wireless device.
It could be possible to evolve existing cellular communications (such as Long Term Evolution; LTE) specifications to include support for Narrowband Internet-of-Things (NB-IoT) technologies. In this respect, the LTE uplink is based on single-carrier frequency-division multiple-access (SC-FDMA) modulation for the uplink data and control channels, and Zadoff-Chu signal for random access. Neither of these signals has good PAPR properties.
Hence, there is still a need for an improved handling of network access for a wireless device in a communications network.